Kaiser Wilhelm the 2nd of Germany had long desired to rule an empire. He thought that Germany needed a powerful Navy to protect it - especially against Britain. The German Navy was set to the ultimate test - war against Great Britain, putting their mighty fleet to good use. They began a naval blockade of Germany during the first days of the war and deployed their naval units. At the outset of World War I, German U-boats, though numbering only 38, achieved notable successes against British warships. By the end of the war Germany had built 334 U-boats and had 226 under construction. The Armistice terms of 1918 required Germany to surrender all its U-boats, and the Treaty of Versailles forbade it to possess them in the future.
When war broke out, only 57 U-Boats were available. He persuaded engineers that more boats were urgently required. Even so, the small, outgunned German fleet managed to strike painful blows to Great Britain by aiming directly for its soft underbelly. The Germans almost succeeded in cutting off Great Britain's shipping lanes, and thus its supply of fuel and raw materials. The German U-boat onslaught against British merchant ships during the autumn of 1940 was highly successful because the attacks were made on the surface at night and from such close range that a single torpedo would sink a ship. Soon, though, Allied technology was able to detect U-boats at night, and new convoy techniques, combined with powerfully-armed, fast modern aircraft searching the seas, meant that by 1941 it was clear that Germany was losing the war at sea.
Winston Churchill anxiously followed the victories and defeats of the U-Boats in the Atlantic. After the war had ended, he admitted that the U-Boat threat had been the one thing that truly scared him during the entire War. The pendulum miraculously swung with improved tactics and technology. In May 1943 out of a force of over 50 U-boats that challenged Convoy ONS5, eight were sunk and 18 were damaged, some seriously. Such losses were unsustainable and, with allied yards turning out ships at ever increasing rates, Donitz withdrew his wolf packs from the North Atlantic. Despite the terrible losses inflicted on the U-boat flotillas, young boys were still attracted to the submarines. As the U-boat memorial near Kiel records, by the end of the war, of the 39,000 men who went to sea in the U-boats, 27,491 died in action and a further 5,000 were made prisoners of war. Of the 863 U-boats that sailed on operational patrols, 754 were lost.